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1.
Débora Danielle Virgínio da Silva Maria das Graças de Almeida Felipe Ismael Maciel de Mancilha Sílvio Silvério da Silva 《Applied biochemistry and biotechnology》2005,121(1-3):427-437
The effect of glucose on xylose-xylitol metabolism in fermentation medium consisting of sugarcane bagasse hydrolysate was
evaluated by employing an inoculum of Candida guilliermondii grown in synthetic media containing, as carbon sources, glucose (30 g/L), xylose (30 g/L), or a mixture of glucose (2 g/L)
and xylose (30 g/L). The inoculum medium containing glucose promoted a 2.5-fold increase in xylose reductase activity (0.582
IU/mgprot) and a 2-fold increase in xylitol dehydrogenase activity (0.203 IU/mgprot) when compared with an inoculum-grown medium containing only xylose. The improvement in enzyme activities resulted in higher
values of xylitol yield (0.56 g/g) and productivity (0.46 g/[L·h]) after 48 h of fermentation. 相似文献
2.
Alves Lourdes A. Vitolo Michele Felipe Maria das Graças A. de Almeida e Silva João Batista 《Applied biochemistry and biotechnology》2002,98(1-9):403-413
The sugarcane bagasse hydrolysate, which is rich in xylose, can be used as culture medium for Candida guilliermondii in xylitol production. However, the hydrolysate obtained from bagasse by acid hydrolysis at 120°C for 20 min has by-products
(acetic acid and furfural, among others), which are toxic to the yeast over certain concentrations. So, the hydrolysate must
be pretreated before using in fermentation. The pretreatment variables considered were: adsorption time (15,37.5, and 60 min),
type of acid used (H2So4 and H3Po4), hydrolysate concentration (original, twofold, and fourfold. concentrated), and active
charcoal (0.5, 1.75 and 3.0%). The suitability of the pretreatment was followed by measuring the xylose reductase (XR) and
xylitol dehydrogenase (XD) activity of yeast grown in each treated hydrolysate. The response surface methodology (24 full factorial design with a centered face) indicated that the hydrolysate might be concentrated fourfold and the pH adjusted
to 7.0 with CaO, followed by reduction to 5.5 with H3PO4. After that it was treated with active charcoal (3.0%) by 60 min. This pretreated hydrolysate attained the high XR/XD ratio
of 4.5. 相似文献
3.
Sene Luciane Felipe Maria G. A. Silva Silvio S. Vitolo Michele 《Applied biochemistry and biotechnology》2001,91(1-9):671-680
Candida guilliermondii FTI 20037 was cultured in sugarcane bagasse hydrolysate supplemented with 2.0 g/L of (NH4)2SO4, 0.1 g/L of CaCl2·2H2O, and 20.0 g/L of rice bran at 35°C; pH 4.0; agitation of 300 rpm; and aeration of 0.4, 0.6, or 0.8 vvm. The high xylitol
production (20.0 g/L) and xylose reductase (XR) activity (658.8 U/mg of protein) occurred at an aeration of 0.4 vvm. Under
this condition, the xylitol dehydrogenase (XD) activity was low. The apparent K
M for XR and XD against substrates and cofactors were as follows: for XR, 6.4×10−2
M (xylose) and 9.5×10−3 mM (NADPH); for XD, 1.6×10−1
M (xylitol) and 9.9×10−2 mM (NAD+). Because XR requires about 10-fold less xylose and cofactor than XD for the condition in which the reaction rate is
half of the V
max, some interference on the overall xylitol production by the yeast could be expected. 相似文献
4.
Rodrigues Denise C. G. A. Da Silva Silvio S. Almeida E Silva J. B. Vitolo Michele 《Applied biochemistry and biotechnology》2002,98(1-9):875-883
Xylose reductase activity of Candida guilliermondii FTI 20037 was evaluated during xylitol production by fed-batch fermentation of sugarcane bagasse hydrolysate. A 24-1 fractional factorial design was used to select process variables. The xylose concentrations in the feeding solution (S
F
) and in the fermentor (S
0), the pH, and the aeration rate were selected for optimization of this process, which will be undertaken in the near future.
The best experimental result was achieved at S
F
=45 g/L, S
0=40 g/L, pH controlled at 6.0, and aeration rate of 1.2 vvm. Under these conditions, the xylose reductase activity was 0.81
U/mg of protein and xylitol production was 26.3 g/L, corresponding to a volumetric productivity of 0.55 g/(L·h) and a xylose
xylitol yield factor of 0.68 g/g. 相似文献
5.
Gimenes Maria Antonieta P. Carlos Luiz Cláudio S. Faria Luís F. F. Pereira Nei 《Applied biochemistry and biotechnology》2002,98(1-9):1049-1059
The global oxygen uptake rate (OUR) and specific oxygen uptake rates (SOUR) were determined for different values of the volumetric
oxygen mass transfer coefficient (15, 43, and 108 h−1), and for varying initial xylose concentrations (50, 100, 150, and 200 g/L) in shaking flasks. The initial cell concentration
was 4.0 g/L, and there was only significant growth in the fermentation with the highest oxygen availability. In this condition,
OUR increased proportionally to cell growth, reaching maximum values from 2.1 to 2.5 g of O2/(L·h) in the stationary phase when the initial substrate concentration was raised from 50 to 200 g/L, respectively. SOUR
showed different behavior, growing to a maximum value coinciding with the beginning of the exponential growth phase, after
which point it decreased. The maximum SOUR values varied from 265 to 370 mg of O2/(g of cell·h), indicating the interdependence of this parameter and the substrate concentration. Although the volumetric
productivity dropped slightly from 1.55 to 1.18 g of xylitol/(L·h), the strain producing capacity (γ
P/X
) rose from 9 to 20.6 g/g when the initial substrate concentration was increased from 50 to 200 g/L. As for the xylitol yield
over xylose consumed (γ
P/S
), there was no significant variation, resulting in a mean value of 0.76 g/g. The results are of interest in establishing
a strategy for controlling the dynamic oxygen supply to maximize volumetric productivity. 相似文献
6.
Faria Luis F. Figueiredo Gimenes Maria Antonieta P. Nobrega Ronaldo Pereira Nei 《Applied biochemistry and biotechnology》2002,98(1-9):449-458
Oxygen availability is the most important environmental parameter in the production of xylitol by yeasts, directly affecting
yields and volumetric productivity. This work evaluated the cell behavior in fermentations carried out with different dissolved
oxygen concentrations (0.5–30.0% of saturation), as well as a limited oxygen restriction (0% of saturation), at several oxygen
volumetric transfer coefficients (12 ≤ k
L
a ≤ 70 h−1). These experiments allowed us to establish the specific oxygen uptake rate limits to ensure high yields and volumetric productivity.
When oxygen availability was limited, the specific oxygen uptake rate values were between 12 and 26 mg of O2/of g cell·h, resulting in a yield of 0.71 g of xylitol/xylose consumed, and 0.85 g/[L·h] for the volumetric productivity.
According to the results, the effective control of the specific oxygen uptake rate makes it possible to establish complete
control over this fermentative process, for both cell growth and xylitol production. 相似文献
7.
Júlio C. Santos Ícaro R. G. Pinto Walter Carvalho Ismael M. Mancilha Maria G. A. Felipe Silvio S. Silva 《Applied biochemistry and biotechnology》2005,122(1-3):673-683
Xylose-to-xylitol bioconversion was performed utilizing Candida guillier-mondii immobilized in sugarcane bagasse and cultured in Erlenmeyer flasks using sugarcane bagasse hydrolysate as the source of xylose.
Fermentations were carried out according to a factorial design, and the independent variables considered were treatment, average
diameter, and amount of bagasse used as support for cell immobilization. By increasing the amount of support, the xylitol
yield decreased, whereas the biomass yield increased. The diameter of the support did not influence xylitol production, and
treatment of the bagasse with hexamethylene diamine prior to fermentation resulted in the highest amount of immobilized cells. 相似文献
8.
Rosa S. M. A. Felipe M. G. A. Silva S. S. Vitolo M. 《Applied biochemistry and biotechnology》1998,(1):127-135
The effect of pH, time of fermentation, and xylose and glucose concentration on xylitol production, cell growth, xylose reductase
(XR), and xylitol dehydrogenase (XD) activities ofCandida guilliermondii FTI 20037 were determined. For attaining XR and XD activities of 129-2190 U/mg of protein and 24-917 U/mg of protein, respectively,
the cited parameters could vary as follows: initial pH: 3.0-5.0; xylose: 15-60 g/L; glucose: 0-5 g/L; and fermentation time:
12-24 h. Moreover, the high XR and XD activities occurred when the xylitol production by the yeast was less than 19.0 g/L. 相似文献
9.
Martínez Ernesto Acosta Silva Silvio S. Felipe Maria G. A. 《Applied biochemistry and biotechnology》2000,84(1-9):633-641
The effect of the oxygen transfer coefficient on the production of xylitol by biocon version of xylose present in sugarcane
bagasse hemicellulosic hydrolysate using the yeast Candiada guilliermondii was investigated. Continuous cultivation was carried out in a 1.25-L fermentor at 30°C, pH 5.5, 300 rpm, and a dilution rate
of 0.03/h, using oxygen transfer coefficients of 10,20, and 30/h. The results showed that the microbial xylitol production
(11 g/L) increased by 108% with the decrease in the oxygen volumetric transfer coefficient from 30 to 20/h. The maximum values
of xylitol productivity (0.7g/[L…h]) and yield (0.58 g/g) were obtained at k
L
a 20/h. 相似文献
10.
Attilio Converti Patrizia Perego José Manuel Domínguez 《Applied biochemistry and biotechnology》1999,82(2):141-151
Three different yeasts, Pachysolen tannophilus, Debaryomyces hansenii, and Candida guilliermondii, were evaluated to ferment xylose solutions prepared from hardwood hemicellulose hydrolysates, among which P. tannophilus proved to be the most promising microorganism. However, the presence of both lignin-derived compounds (LDC) and acetic acid
rendered a poor fermentation. To enhance the fermentation kinetics, different treatments to purify the hydrolysates were studied,
including overliming, charcoal adsorption for LDC removal, and evaporation for acetic acid and furfural stripping. Under the
best operating conditions assayed, 39.5g/L of xylitol were achieved after 96 h of fermentation, which corresponds to a volumetric
productivity of 0.41 g/L·h and a yield of product on consumed substrate of 0.63 g
p
/gS. 相似文献
11.
Ernesto Acosta Martínez Silvio S. Silva Maria G. A. Felipe 《Applied biochemistry and biotechnology》1999,77(1-3):347-354
The biocon version of xylose intoxylitol using pH values of 4.0, 5.5 and 7.0 and tetracycline concentrations of 20 and 40
mg/L was carried out to verify the influence of these parameters on Candida guilliermondii metabolism for xylitol production. Experiments were performed with sugarcane bagasse hemicellulosi chydrolysate (48.5 g/L
of xylose) in 125-mL Erlenmeyer flasks, at 30°C, 200 rpm, during 88 h. The results demostrated that the bioconversion of xylose
into xylitol was significantly influenced by the pH. On the other hand, in media containing 20 or 40 mg/L of tetracycline,
this bioconversion was not significantly affected. The best results of xylitol production were obtained in hemicellulosic
hydrolysate without tetracycline, at pH 7.0 In these conditions, the maxim um specific growth rate was 0.014/h and the yield
factor of xylitol and volumetric productivity were 0.85g/g and 0.70g/L/h respectively. Xylitol and cell growth occureed simultaneously. 相似文献
12.
Inês C. Roberto Ismael M. de Mancilha Sunao Sato 《Applied biochemistry and biotechnology》1999,77(1-3):205-210
The fermentation kinetics for the conversion of rice straw hemicellulosic hydrolysate to xylitol by the yeast Candida guilliermondii was evaluated under batch conditions. The fermentation was accomplished in a 1 L working volume stirred-tank reactor with
aeration of 1.3 vvm and agitation of 300 rpm (kLa=15/h). The maximum specific rate of xylitol formation (0.12 g/g) was achieved when the specific growth rate was lowered
to 1/5 of its highest value. From analysis of the fermentation kinetics, a linear correlation between specific growth rate
(μx) and specific rate of xylitol formation (qp) was evident. Based on the Gaden model, this bioprocess was classified as growth-associated production and the relationship
between μx and qp can be described by the equation qp=6.31μx. 相似文献
13.
Rafael Fogel Rafaela Rodrigues Garcia Rebeca da Silva Oliveira Denise Neves Menchero Palacio Luciana da Silva Madeira Nei Pereira Jr. 《Applied biochemistry and biotechnology》2005,122(1-3):741-752
The dilute-acid hydrolysis of sugarcane bagasse was optimized using a statistical experimental design resulting in hydrolysates
containing 57.25 g/L of xylose, which were fermented with a high inoculum concentration (10 g/L of the yeast Candida guilliermondii IM/UFRJ 50088). The addition of urea reduced the time of conversion (t
C) to 75 h (without nitrogen source addition t
C>127 h), and, consequently, improving the rates of xylitol bioproduction. Fermentator experiments, using the optimized conditions,
resulted in enhanced conversion rates, reducing t
C to 30 h. The stability of the yeast in the hydrolysate was also verified in a 480-h cultivation. 相似文献
14.
Rodrigues Denise C. G. A. Suva Silvio S. Prata Arnaldo Marcio R. Felipe Maria das Gracas A. 《Applied biochemistry and biotechnology》1998,(1):869-875
Batch, fed-batch, and semicontinuous fermentation processes were used for the production of xylitol from sugarcane bagasse
hemicellulosic hydrolysate. The best results were achieved by the semicontinuous fermentation process: a xylitol yield of
0.79 g/g with an efficiency of 86% and a volumetric productivity of 0.66 g/L/h. 相似文献
15.
Domínguez JM Cruz JM Roca E Domínguez H Parajó JC 《Applied biochemistry and biotechnology》1999,81(2):119-130
Debaryomyces hansenii cells were entrapped in Ca-alginate beads and used for producing xylitol from wood hydrolyzates. Batch experiments showed
that bioconversion was severely hindered when Ca-alginate beads were hardened with Al3+ solutions. As an alternative to Al3+ hardening, the improvements in both mechanical stability of bioparticles and fermenting ability of the immobilized system
derived from using increased concentrations of sodium alginate were assessed. The best results were obtained using a 4% (w/v)
Na-alginate solution in the gelification step. This concentration was selected to perform continuous fermentations in a packed-bed
reactor using raw or charcoal-treated hydrolyzates (15.5 g of xylose/L) with two different yeasts: Candida guilliermondii and Debaryomyces hansenii. With a final cell concentration of about 50 g of cells/L (0.075 g of cells/g of beads), the volumetric productivities reached
with these yeasts in media made from charcoal-treated hydrolyzates were 0.58 and 0.91 g/L·h, respectively. 相似文献
16.
Mayerhoff Zea D. V. L. Roberto Inês C. Franco Telma T. 《Applied biochemistry and biotechnology》2001,91(1-9):729-737
Xylose reductase (XR) activity was evaluated in extracts of Candida mogii grown in media containing different concentrations of rice straw hydrolysate. Results of X Ractivity were compared to xylitol
production and a similar behavior was observed for these parameters. Highest values of specific production and productivity
were found for xylose reductase (35 U/g of cell and 0.97 U/[g of cell·h], respectively) and for xylitol (5.63 g/g of cell
and 0.13 g/[g of cell·h]) in fermentation conducted in medium containing 49.2 g of xylose/L. The maximum value of XR:XD ratio
(1.82) was also calculated under this initial xylose concentration with 60 h of fermentation. 相似文献
17.
Eliana V. Canettieri João B. Almeida E. Silva Maria G. A. Felipe 《Applied biochemistry and biotechnology》2001,94(2):159-168
This study deals with the bioconversion of xylose into xylitol by Candida guilliermondii FTI 20037 using eucalyptus hemicellulosic hydrolysate obtained by acid hydrolysis. The influence of various parameters (ammonium
sulfate, rice bran, pH, and xylose concentration) on the production of xylitol was evaluated. The experiments were based on
multivariate statistical concepts, with the application of factorial design techniques to identify the most important variables
in the process. The levels of these variables were quantified by the response surface methodology, which permitted the establishment
of a significant mathematical model with a coefficient determination of R
2=0.92. The best results (xylitol=10.0 g/L, yield factor=0.2 g/g, and productivity=0.1 g/[L·h]) were attained with hydrolysate
containing ammonium sulfate (1.1 g/L), rice bran (5.0 g/L), and xylose (initial concentration of 60.0 g/L), after 72 h of
fermentation. The pH of fermentation was adjusted to 8.0 and the inoculum level utilized was 3 g/L. 相似文献
18.
Silva Silvio S. Ribeiro JoÃo D. Felipe Maria G. A. Vitolo Michelle 《Applied biochemistry and biotechnology》1997,(1):557-564
Batch fermentations of sugar cane bagasse hemicellulosic hydrolysate treated for removing the inhibitors of the fermentation
were performed byCandida guilliermondii FTI20037 for xylitol production. The fermentative parameters agitation and aeration rate were studied aiming the maximization
of xylitol production from this agroindustrial residue. The maximal xylitol volumetric productivity (0.87 g/L h) and yield
(0.67 g/g) were attained at 400/min and 0.45 v.v.m. (KLa 27/h). According to the results, a suitable control of the oxygen input permitting the xylitol formation from sugar cane
bagasse hydrolysate is required for the development of an efficient fermentation process for large-scale applications. 相似文献
19.
We changed the fluxes of xylose metabolites in recombinant Saccharomyces cerevisiae by manipulating expression of Pichia stipitis genes (XYL1 and XYL2) coding for xylose reductase (XR) and xylitol dehydrogenase (XDH), respectively. XYL1 copy number was kept constant by integrating it into the chromosome. Copy numbers of XYL2 were varied either by integrating XYL2 into the chromosome or by transforming cells with XYL2 in a multicopy vector. Genes in all three constructs were under control of the strong constitutive glyceraldehyde-3-phosphate
dehydrogenase promoter. Enzymatic activity of XR and XDH in the recombinant strains increased with the copy number of XYL1 and XYL2. XR activity was not detected in the parent but was present at a nearly constant level in all of the transformants. XDH activity
increased 12-fold when XYL2 was on a multicopy vector compared with when it was present in an integrated single copy. Product formation during xylose
fermentation was affected by XDH activity and by aeration in recombinant S. cerevisiae. Higher XDH activity and more aeration resulted in less xylitol and more xylulose accumulation during xylose fermentation.
Secretion of xylulose by strains with multicopy XYL2 and elevated XDH supports the hypothesis that d-xylulokinase limits metabolic flux in recombinant S. cerevisiae. 相似文献
20.
Inhibition of microbial xylitol production by acetic acid and its relation with fermentative parameters 总被引:5,自引:0,他引:5
Precipitated sugarcane bagasse hemicellulosic hydrolysate containing acetic acid was fermented by Candida guilliermondii FTI 20037 under different operational conditions (pH 4.0 and 7.0, three aeration rates). At pH 7.0 and k
L
a of 10 (0.75 vvm) and 22.5/h (3.0 vvm) the acetic acid had not been consumed until the end of the fermentations, whereas at
the same pH and k
L
a of 35/h (4.5 vvm) the acid was rapidly consumed and acetic acid inhibition was not important. On the other hand, fermentations
at an initial pH of 4.0 and k
L
a of 22.5 and 35/h required less time for the acid uptake than fermentations at k
L
a of 10/h. The acetic acid assimilation by the yeast indicates the ability of this strain to ferment in partially detoxified
medium, making possible the utilization of the sugarcane bagasse hydrolysate in this bioprocess. The effects on xylitol yield
and production are reported. 相似文献